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Feedback HDRP - Physical Light Values Seems Incorrect

Discussion in 'Graphics Experimental Previews' started by Grimreaper358, Oct 24, 2019.

  1. Grimreaper358

    Grimreaper358

    Joined:
    Apr 8, 2013
    Posts:
    789
    Working with actual Physical light values in HDRP doesn't give the results expected.

    TLDR: Directional and Ambient lighting doesn't work well with punctual lights when using physical values (Sunny 16). When lighting a scene with exterior and the interior lighting they don't work well together using physical values. Each scenario by itself works fine but as soon as you try to do both in a scene, the punctual lights lighting is non-existent until you turn up the intensity of the lights (Point, Spot, Area, Emissive, VFX, etc) to 30,000+ Lumens or 9 Ev (Dark areas/Interior). (You can get the two to work together if you use custom values for lighting)

    Almost a year and a half ago I watched a video on UE4's physical Lights implementation in UE4.19 and it had the same issue. Not sure if both are based on the same material but I didn't expect to come across the same issue with HDRP.

    Known Issue?
    When the new post-processing was first available earlier this year in January, I noticed an issue with lighting when trying to use both directional and punctual lights to do lighting (interior and exterior) in a scene with physical light values. I was waiting to see if there would be a fix for it, but I haven't seen anything related to it on Github or that this was an issue anywhere. Basically, it works but in opposite scenarios. For instance, If you do exterior lighting (day) the interior lights with physical values will be really dim. If you do a night scene then the interior lights with physical values work as they should since the directional light if any at most would be the brightness of the moon and that wouldn't overpower the local lights. This affects VFX as well since they use emission for lighting.

    Is it because the post-processing side of things came in later than lights using physical values? Before the new post-processing, directional lights would only go up to 10k Lux (with PPV2) so maybe the punctual lights and emissive lights didn't get scaled for the new post-processing as well? Maybe it's the exposure values that only became wider so we are able to have higher intensity lights but isn't coherent with lower light intensity?

    I've been mainly working with exterior/day scenes so I didn't check back to see if this was solved until now.

    Example - Day (Baked Directional Light for Indirect Lighting)

    Physical Light Units
    Sky - 15.5 Ev
    Sun - 80k Lux
    Punctual Lights Interior - 1200 Lumens

    Camera (Settings used to match the auto-exposure with instead of eyeballing. Still a slight difference)
    ISO - 100
    Shutter Speed - 125
    Aperture - 14

    Auto Exposure (this is the exposure used as the physical camera vales don't auto expose)
    Exposure Max - 14.6 Ev

    You can't see the interior lights as they would actually be



    Now If I turn up the intensity of the interior lights to 100k Lumens then you will be able to see them slightly
    Same settings as above just the interior lights got increased to 100k Lumens




    Video Mentioned in TLDR (Timestamped showing the same issue) -